SH7020 Datasheet, PDF (450/509 Pages) Renesas Technology Corp – SuperH™ RISC engine

18.4.3 Standby Mode Application
In this example, the standby mode is entered on the falling edge of the NMI signal and canceled
on the rising edge of the NMI signal. Figure 18.1 shows the timing.
After an NMI interrupt is accepted (high goes to low) while the NMI edge select bit NMIE in the
interrupt control register ICR is cleared to 0 to select detection of the falling edge, the NMI
exception service routine sets the NMIE to 1 (selecting detection of the rising edge) and sets the
SBY bit to 1. Finally, it executes a SLEEP instruction to enter the standby mode.
The standby mode is canceled on the rising edge of the NMI signal.
Oscillator
CK
NMI
NMIE
SSBY
Clock setting time
NMI Exception
exception service
processing routine
SBY = 1
SLEEP
instruction
Standby Oscillation
mode start
time
Time
set
in
WDT
NMI
exception
processing
Figure 18.1 NMI Timing for the Standby Mode (Example)
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